Electric switch and contact structure therefor



y- 1931- w. R. MANN w 1,816,052 ELECTRIC SWITCH AND CQNTACT STRUCTURE THEREFQR Filed Nov. :0. 192a MANUFACTURING CORPORATION,

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fatentecl July 28, 193i f UNITED. STATES PATENT ()FFICE WILLIAM R. MANN, OF SHARON, MASSACHUSETTS, ASSIGNOR TO CONDIT ELECTRICAL RATION OF MASSACHUSETTS OF SOUTH BOSTON, MASSACHUSETTS, A CORPO- ELECTRIC SWITCH AND CONTACT STRUCTURE- THEREFOR Application file d November 30, 1928. Serial No. 322,686.

This invention relates to electric switches and particularly to switches wherein laminated'brush members are carried by and electrically connected with the lower ends of 45 spaced stationary switch members and has for an object the provision of means to improve the contact therebetween. fIt is the practice to provide the current conducting studs with screw-threaded end portions on'whi'ch to support the laminated brush members between a pair of spaced clamping nuts. The individual lamina, and especially the intermediate laminae of the brush consequently make little or no direct contact with the stud, and the current flowing through the switch passes transversely through the brush, or across the superposed laminae thereof, to .the outer laminae. Thus the current path through the intermediate laminae includes one or more of the high resistance contact j unctionsbetween plates, each of which offers considerable resistance to the passage of current. As a result considerable heat is generated in the brush which in turn 5 causes 'oxidization of the contacting surfaces of the laminae and further increases the heating of the brush. Frequently, the temper of the'brush lbecomes destroyed due to the heat generated therein and the-brush is unable to maintain the necessary contact pressure, re-

sulting in arcing at'the contact faces which soon renders the switch inoperative.

An' object of this invention is to provide a contact structure especially of the inverted brush type'wherein each lamina of the brush provides a separate low resistance path between the movable switch member and its supporting stud. Y

A further object of the invention is to provide an inverted brush structure inwhi'ch each lamina of the brush has a section thereof in pressureengagement with itssupporting and conducting stud.

A still further object is to provide a brush structure in which each lamina of the brush hasan edgewise contact area in engagement with its supporting stud which area is at least as great as the cooperating contact face of the lamina.

-,A still further object is to provide. an infor the brush members.

constructed in accordance with the invention.

For purposes of illustration the invention is embodied in a down break electric switch, only that part of the switch being shown which is necessary to disclose the invention.

As herein shown, the stationary switch members include the conducting studs and 12, which are disposed within and supported by the spaced insulating bushings 14 and 16. Laminated brush members 18 and 20 are fixed detachably to the lower extended ends of said studs 10 and 12 in a manner hereinafter described, which studs thus constitute holders Said brush mem bers 18 and 20 are of the inverted, non reactive, type and comprise a plurality of superposed lamina of resilient conducting material, each having a horizontal support ing section 22 and an angularly related -depending toe section 24E. Said toe sections are directed downwardly and inwardly toward each other and terminate in substantially horizontal contact faces 26 which are disposed in a position to be bridged by the movable switch member.

Said movable switch member includes the vertically reciprocable switch operatingrod 28 of wood or other suitable insulating inate rial having a metal ferrule 30 secured fixedly to its lower end to which the movable contact bridging member 32 is pivotally secured by means of a pin 34:. Outstanding flanges 86 on said ferrule 30 overlie the upper surfaces of said bridging member 32 and are slightly spaced therefrom whereby to limit the pivotal movement of said bridging member on said pin 34. Said bridging member 32 is provided with flat contact faces 38 at either end which are adapted to engage the horizontal contact faces 26' of the stationary brush members 18 and 20 when the movable switch member is moved upwardly into the switch closed position shown in Fig. 1.

According to the present invention the conducting studs 1 .0 .and 12 are provided with downwardly tapered brush supporting porshoulder 48 formed by the reduced end portions 40 and reduced screw threaded end portions 42 therebeneath. Said studs are fun ther provided with screw threads 44: above said tapered portions 40, and nuts 46 are threaded thereon in position to bear against the lower ends of bushings '14 and 16, where by to prevent upward movement of the studs in the bushings. Thebrush supporting actions 22 of the brush members 218 and are provided with correspondingly tapered holes to receive the tapered portions of said studs 1-0 and .12 closely therewithin, whereby to bring a sectional area of each lamina of the brush into contact with the stud.

Clamping nuts 47 are screw threaded-on said .lower reduced end portions l2 whereby to clamp each lamina of the brush members forcibly against the tapered portions 40 of said studs. When clamped in position on the tapered portions 40 of the studs the brush members are arranged to be situated below and slightly spaced from the nuts 4.6 and are also arranged to extend somewhat below the direct pressurecngaging relation with its supporting stud whereby each provides a separate current con-ducting path between its supporting stud and the movable bridging member 32, irrespective of the otherlaminae of the brush, thus eliminating from the cirsuit the resistance of the surface contact junctions "between adjacent laminae of the brushes. Each lamina has a cross sectional area thereof in intimate contact with the tapered portion 40 of the stud, which area is at least as great as the area of its contact face 26 and provides an individual current =conducting path independent of the adjacent laminae. Since a low resistance path is provided, little or no current willpass laterally through the brush from one to the otherjof the laminae and the heating of the brush memher is largely eliminated. This is a distinct advantage over the prior art wherein the laminated brush member was received loosely on a straight screw threaded portion of the stud isms-5s and, at most, only a casual connection eX'- isted between the intermediate laminae and the tops of the screw threads on the stud.

To assist in conducting the current from the inner to the outer laminae, which were the only ones having good electrical connection with the stud, it was formerly necessary to solder the horizontal supporting sections of the la-mime together This resulted in a brush so stiff that stubbing occurred at the cooperating contact face. This trouble is entirely obviated by the present invention. Since each lamina of the brush provides an individual current path to the stud, it is unnecessary to connect the horizontal supporting sections 22 electrically, thus greatly increasing the flexibility .of the brush without increasing the lateral spacing of the stationary switch members. A jacket 52 maybe provided about the horizontal supporting section22 to form a convenient unitary brush structure, but with the tapered brush and stud construction set forth the several laminae are free to flex slightly, thus greatly improvthe operation of the switchand particularly the contact members thereof.

The construction may be modified in many ways without departing from the scope of the invention. 7

I claim: a

L In an electric switch, the combination of .a brush holder, a laminated brush member having .a passage therethroug-h which .is so formed that the laminae have tapered faces in said passage, and meansconnected with said holder located in said-passage andhavi-ng a surface corresponding with and in indepen dentengagement with the tapered faces of the laminae. 1 I

2.1n an electric switch, the combination of a brush holder, a laminated brush memher having a tapered passage therethrough, and means-connected with saidbrush holder having a tapered section conformed with and received in'said tapered passage and making independent contact with each brush lamina.

' 3. In an electric switch thecombination of a current conducting stud having a tapered lower end portion, :a laminated brush member carried by said stud, each lamina having a correspondingly tapered passage therethrou-gh, the side walls of which abut against the tapered portion of said stud, :andpres sure applying means arranged to urge the V tapered side walls of said laminae into curaxially of said stud arranged :to urge each ofthe lamina of said brush firmly against the tapered portionof said stud, wherebyito pro- Cfl vide a separate current conductingpath from said stud through each lamina of said brush.

5. In an electric switch, the combination of a current conducting stud having a tapered lower end portion, a laminated brush member having a correspondingly tapered passage through the laminae thereof and adapted to be received on the tapered portion of said stud, and means to clamp said brush member against the taper of said stud arranged to maintain edgewise contact between each lamina thereof and the tapered portion of said stud.

In testimony whereof, I have signed my name to this specification.

WILLIAM R. MANN. 

